Apparatus for ladling liquid metal



Oct. 7, 1969 P. R. SOLHEIM APPARATUS FOR LADLING LIQUID METAL 3Sheets-Sheet 1 Filed Nov. 30, 1967 In; 4 Fm; 7 4 1 1 I u 2 i 5 8 l. 3 29 .1 Q G Cl u v. V/

INVENTOR P w B ATTORNEYS Oct. 7, 1969 P. R. sou-lam 3,471,057

APPARATUS FOR LADLING LIQUID METAL 3 Sheets-Sheet 3 Filed Nov. 30, 1967INVENTOR PE DER mamvmo- SOME/N BY ATTORNEYS United States Patent Int.01. B67d 5/54, 5/50 US. Cl. 222-61 2 Claims ABSTRACT OF THE DISCLOSUREApparatus for ladling of liquid metal having a reservoir of liquid metalwith a discharge chamber submerged therein having a gas inlet and anoutlet for metal. A source of gas under pressure is connected with thegas inlet and a first conduit rises with is upper end into the dischargechamber to a level above said outlet. The lower end extends down intothe reservoir to a depth at which the static pressure is above apredetermined maximum gas pressure to be applied in the dischargechamber during operation. A discharge spout is provided with a secondconduit connecting the outlet with such spout. A valve connects in oneposition the discharge chamber with the source of gas under pressure andin a second position connects the discharge chamber with a lowerpressure. Activating means for the valve are provided with meansconnecting the activating means with the gas in the discharge chamber.The activating means moves the valve from the first-mentioned positionto the second position when the gas pressure in the discharge chamberreaches the predetermined maximum gas pressure. Means for returning thevalve to the first-mentioned position are provided. The second conduitis a U-shaped tube and that part of the U-shaped tube at which the levelof the metal in the tube will be positioned at the end of a ladling hasa reduced cross sectional area.

The invention relates to liquid metal ladling, and more particularly toa process and an apparatus for discharging or ladling controlledquantities of liquid light metal, such as magnesium and aluminum andalloys based on one of these metals, from a reservoir such as, forexample, a melting furnace.

The ladling of controlled quantities of liquid metal to metal castingmachines is an operation of increasing importance in the field of metalcasting, which in a considerable measure is due to the development ofmetal casting machines adapted for mass production. Perhaps especiallyin connection with the die casting of light metals, a need is felt foran improved accuracy in the ladling of a predetermined volume, in thesense that a more narrow range of deviation is required in therepetitive ladling of the predetermined volume.

A number of different ladling devices for liquid metal are known, seefor instance a survey given in Gie'sserei 49 (1962) 8, p. 180-189, amongwhich are devices comprising a valve-less discharge chamber, whichchamber during operation dips into the reservoir of liquid metal to beladled. The invention relates to a device of this type.

Such devices comprise a discharge chamber or crucible intended to dipinto the liquid metal reservoir, the discharge chamber being providedwith means for introducing pressure gas to expel liquid metal out fromthe discharge chamber, an inlet passage to permit liquid metal to flowfrom the reservoir into the discharge chamber, the inlet passageterminating at its upper end above the bottom of said chamber andextending into said reservoir of metal to a depth at which the pressureis equal to or higher than the maximum gas pressure to be applied in thedischarge 3,471,057 Patented Oct. 7, 1969 chamber during operation, anda discharge tube which inside the discharge chamber terminates at alower level than said inlet passage.

According to a known mode of operating a ladling apparatus of theabove-mentioned type, the quantity of metal discharged is controlled byfirst applying a relatively low gas pressure to bring the level ofmolten in the discharge chamber to a discharge starting level, whereuponmolten metal is discharged by applying a predetermined higher gaspressure during a predetermined time interval.

One of the objects of the present invention is to provide a liquid metalladling apparatus enabling a very high accuracy to be convenientlyachieved in the repetitive ladling of a predetermined volume of liquidmetal to moulds or other casting devices, such as a die casting machine.

The above and other objects and features of the invention will be morereadily apparent from the following description when read in connectionwith the accompanying drawings, in which:

FIG. 1 is a diagrammatic side view, partially in section, of a containerholding a liquid metal reservoir, with ladling apparatus embodying theinvention;

FIG. 2 is a view similar to that of FIG. 1 but showing a furtherembodiment;

FIG. 3 is a view similar to that of FIG. 1 showing an embodiment of theapparatus assembled with an instrumentation suitable for use inautomatic operation.

In FIG. 1 of the drawing, 1 is a container or reservoir holding themolten metal to be ladled. This container 1 can be of any suitabledesign and very often will be a holding furnace or the like (thoughheating means are not shown in the drawing). A discharge chamber orcrucible 2 has an inlet conduit 3 allowing molten metal to flow into thechamber 2 from the container 1. A discharge conduit 23 has an inlet arm5 projecting upwardly into the lower portion of the chamber 2, and adischarge arm 4 that opens into a discharge chute 6 serving to conductthe discharged metal to the point of use. Below the chamber 2 the arm 5has a part 5a having a reduced cross sectional area. 4a designates asimilar part of the arm 4 at or near the level of the molten metal inthe container 1. A conduit 7 is connected to the discharge chamber 2communicating with a source of pressure gas, and a branch conduit 8provides communication between the discharge chamber 2 and a pressurecontroller 9.

The apparatus shown in FIG. 2 is similar to that of FIG. 1 except thatthe discharge tube consists of two separate parts 24 and 25, whichcorrespond to the arms 4 and 5 of the U-shaped tube 23 in FIG. 1 andwhich can together function like a U-shaped tube, one arm 24 beingplaced inside the other arm 25. Therefore, this construction can beconsidered as a U-shaped tube, since for the purposes of the inventionit has the function of a U- shaped tube. This particular construction ofthe discharge tube presents constructional advantages and facilitatesdraining and cleaning operations.

The process and apparatus of the invention Will now be further explaineddescribing ladling operations with reference to the embodimentillustrated in FIG. 3. In this example the discharge chamber 2 issubmerged in the molten metal reservoir, and the level of the moltenmetal as well as the gas pressure, conveniently atmospheric, are thesame outside and inside of the discharge chamber 2.

At the arrival of a mould at the remote end of the discharge chute 6,the following sequence of events will take place (details of the mode ofoperation of the instrumentation shown in FIG. 3 will be explainedbelow).

Pressure gas is supplied to the chamber 2 via conduit 7 and the metallevel in the chamber 2 is depressed. The metal displaced flows to thereservoir in the container 1 reaches the upper edge of the conduit 3,the level of the' molten metal in the discharge tube 33 will still bethe same as that of the reservoir in the container 1. As pressure gascontinues to flow into the chamber 2 the level of the molten metaltherein is continuously further depressed, and the metal in thedischarge tube 33 will now rise rapidly and molten metal will bedischarged into the chute 6 to flow to the mould. When the level of themetal in the chamber 2 is level with the upper edge of the tube arm 35the main portion of the discharge volume has been expelled. Inaccordance with a preferred embodiment of the invention, the level ofthe molten metal in chamber 2 is depressed down into the tube arm 35,for instance to a level indicated by a-a in the drawing. This level willcorrespond to a certain gas pressure in the chamber 2 and in thepressure controller 9. By means of an instrumentation as illustrated inFIG. 3, and which forms no part of this invention, the gas flow isreversed so that gas is released from the discharge chamber 2, causingthe metal level in tube arm 34 to immediately drop below dischargelevel.

As the gas pressure in the chamber 2 drops toward the initial lowpressure (in this example atmospheric pressure), the chamber 2 will berefilled with molten metal from the reservoir in container 1 via conduit3. A discharge cycle has now been completed, and the next cycle isinitiated, conveniently, as known, by the next mould as it arrives toreplace the preceding mould.

Adjustment of a particular discharge starting level below the overflowlevel at the upper edge of conduit 3 for example by means of apredetermined low gas pres sure as used conventionally-requires thatmuch extra control equipment, and, besides, a certain time interval isnecessary for such adjustment. In the mode of operation described above,wherein the discharge starting level is automatically self-establishedas a result of overflow into conduit 3, each discharge cycle can be madevery short, resulting in greater discharge capacity per hour.

The inlet conduit 3 extends to a depth in the reservoir of container 1at which the hydrostatic pressure is sufficicntly high to prevent gasfrom blowing past at any time during discharge operations. An inletconduit 3 without sectional restriction can then be used, which permitsrapid refilling of the chamber 2.

The cycle discharge volume will chiefly depend on the dimensions ofchamber 2 and the vertical distance from the upper edge of inlet conduit3 to the upper edge of tube arm 35 (or tube arm 5, FIG. 1 or tube 25,FIG. 2). However, using the apparatus of the invention the desireddischarge volume can be varied or adjusted within certain limits byadjusting the discharge terminating level a-a in tube arm 35, which iseffected by correspondingly adjusting the pressure at which pressurecontroller 9 will actuate pressure release in chamber 2.

Small variations in the discharge volume will systematically result fromvariations in the level of the molten metal in container 1 under theconditions assumed in the example above, i.e. using as dischargestarting level the overflow level as determined by the upper edge ofinlet conduit 3. However, these variations in the discharge volume canbe made quite insignificant by (1) maintaining a fairly constant moltenmetal level in the container 1, and (2) using a discharge tube ofmoderate cross section or, if desired, merely reducing the cross sectionof that portion of 4a of tube arm 4 (FIG. 1), which is level with themolten metal in the container 1, the reduced cross section beingprovided over a vertical length sufficient to cover said variations inthe metal level in container 1. These systematic variations in thedischarge volume will vary proportionally with said cross section underthe conditions assumed in the above example.

Variations in the discharge volume will also result from variations inthe predetermined gas pressure at 4 which discharge is terminated. Thesevariations as well can be made quite insignificant, by

(1) using accurate pressure control equipment to actuate dischargetermination, and

(2). providing a discharge tube having a reduced cross section in thatportion 5a of tube arm (FIG. 1) where the metal meniscus will be at themoment of discharge termination.

The cross section of the discharge tube above and below theabove-mentioned portions will not affect the ladling volume accuracy,and practically it will be advantageous to provide a discharge tubehaving a considerable cross section above and below the above-mentionedportions in order to reduce pressure drop in the discharge tube, whichis particularly desirable when short cycles are required.

The process and apparatus of this invention has proven to be capable ofvery accurate and rapid and otherwise satisfactory ladling.

The discharge tube should not extend unnecessarily far above the moltenmetal level in container 1, since (unless special precautions are taken)this would result in undesirable breathing, that is sucking in andblowing out of the gas present in the chute 6. This gas mayadvantageously consist of or contain an inert gas.

It will readily be understood that the inlet conduit and the dischargeconduit need not have the form of a tube in a narrow sense of the word,but can be passages or conduits of any suitable shape.

Finally, the instrumentation shown in FIG. 3 will now be explained. Theabove-mentioned pressure controller 9, which can be of any suitabletype, has been shown as comprising a U-shaped tube, which containsmercury. This tube communicates with the discharge chamber 2 via aconduit 8. A pressure tank 10 contains pressure gas, which, if desired,can be an inert gas such as argon; 11 is a high pressure gas container,and 12 is a pressure reducing valve providing a constant pressure in thetank 10; 13 is a pipe and 14 is a throttle valve. The discharge rate canbe controlled by means of this valve. 15 is a 3-way solenoid valveprovided with a spring return 15a, solenoid 15b and ports 0, d and e; 16and 17 are pipes and 18 is a throttle valve; 19 is a source of electriccurrent and 20 is a starting switch; 21 is a master relay which whenengaged will connect the circuit with solenoid 15b across a set ofcontacts b. A set of contacts a serve as holding contacts for the relaysolenoid 21. 22 is an auxiliary relay, which will break the circuit tothe relay 21 when the current is supplied thereto via connection point9a of the pressure controller 9, via the mercury to the adjustableelectrode 9b.

A discharge cycle is started by engaging the switch 20 for a moment(preferably by means of an automatic impulse). Master relay 21 will thenreceive electric current and engage contacts a and b. Now solenoid 15bwill receive current to close port e, while ports 0 and d areinterconnected to permit gas to flow from tank 10 to the dischargechamber 2. The ladling now proceeds as already described above. At acertain gas pressure in conduit 8 which corresponds to the desired levelof the molten metal in tube arm 35, contact is established between themercury and the electrode 9b, and relay 22 will break the holdingcurrent to master relay 21 causing the latter to disconnect, whereby thecurrent to solenoid 15b is broken so that the discharge valve 15 returnsto normal position due to the spring 15a. Thereby the gas supply fromtank 10 is stopped and the chamber 2 is evacuated via ports d and e,either directly to the atmosphere or, as shown in FIG. 3, to the chute6, the latter being preferable when the gas employed is a more or lesspure inert gas, which can thus be utilized further as a protective gasfor the metal in the exit portion of the tube arm 34 and adjacent parts.

I claim:

1. Apparatus for ladling of liquid metal comprising a reservoir ofliquid metal, a discharge chamber submerged in said reservoir having agas inlet and an outlet for metal, a source of gas under pressure, meansconnecting said source with said gas inlet, a first conduit rising withits upper end into said discharge chamber to a level above said outletand with its lower end extending down into said reservoir of liquidmetal to a depth at which the static pressure is aljpve a predeterminedmaximum gas pressure to be applied in said discharge chamber duringoperation, a discharge spout, a second conduit connecting said outletwith said spout, a valve connecting in one position said dischargechamber with said source of gas under pressure in a second positionconnecting said discharge chamber with a lower pressure, activatingmeans for said valve, means responsive to the pressure of the gas insaid discharge chamber controlling said activating means, saidactivating means moving said valve from the first-mentioned position tosaid second position when the gas pressure in said discharge chamberreaches said predetermined maximum gas pressure, and means for returningsaid valve to the first-mentioned position.

2. Apparatus as claimed in claim 1 wherein said second conduit is aU.-shaped tube and wherein that part of said U-shaped tube at which thelevel of the metal in the tube will be positioned at the end of aladling has a reduced cross sectional area.

References Cited UNITED STATES PATENTS ROBERT B, REEVES, PrimaryExaminer H. S. LANE, Assistant Examiner US. Cl. X.R. 280-515

